Implant peg with multiple components

ABSTRACT

An implant system comprises an implant plate adapted to be positioned on a surface of a resected bone. The implant plate has a plurality of openings. A plurality of independently positionable pegs attach the implant plate to the bone. Each peg has a longitudinal axis and comprises: a peg body and a retaining device. The peg body is inserted into a peg hole in the bone. The peg body has a transverse dimension in a direction normal to the longitudinal axis, the transverse dimension larger than the openings of the plate. The retaining device is separate from the peg body, and is configured to attach to the peg body, with at least a first portion of the retaining device positioned above an upper surface of the implant plate, and a connecting portion of the retaining device extending through one of the openings of the implant plate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase entry under 35 U.S.C. 371 ofinternational patent application No. PCT/US2016/055514, filed Oct. 5,2016, the entirety of which is incorporated herein by reference.

FIELD

This disclosure relates generally to medical devices, and specificallyto bone implants.

BACKGROUND

An ankle joint may become severely damaged and may be treated by totalankle replacement. One type of total ankle replacement comprises twocomponents; one part is implanted in a resected tibia and the other partis implanted in a resected talus. The talar implant can include a stemand/or one or more pegs, screws or combinations of pegs, screws and stemthat extend into openings drilled into the resected surface of the bone.In some patients, the quality of the bone into which the pegs are to beinserted is poor.

SUMMARY

In some embodiments, an implant system comprises an implant plateadapted to be positioned on a surface of a resected bone. The implantplate has a plurality of openings therethrough. A plurality ofindependently positionable pegs are provided for attaching the implantplate to the resected bone. Each peg has a longitudinal axis andcomprises: a peg body and a retaining device. The peg body is adapted tobe inserted into a respective peg hole in the resected bone. The pegbody has a transverse dimension in a direction normal to thelongitudinal axis, the transverse dimension larger than the plurality ofopenings. The retaining device is separate from the peg body. Theretaining device is configured to attach to the peg body, with at leasta first portion of the retaining device positioned above an uppersurface of the implant plate, and a connecting portion of the retainingdevice extending through one of the openings of the implant plate.

In some embodiments, an implant system comprises an implant plateconfigured to be positioned on a surface of a resected bone. The implantplate has a plurality of openings therethrough. A plurality ofindependently positionable pegs are provided for attaching the implantplate to the resected bone. Each peg has a longitudinal axis andcomprises: a peg body and a retaining device. The peg body is adapted tobe inserted into a respective peg hole in the resected bone. The pegbody has a transverse dimension in a direction normal to thelongitudinal axis. The transverse dimension is larger than a diameter ofat least one of the plurality of openings. The peg body furthercomprises a proximal connecting portion penetrating one of the openingsof the implant plate. The retaining device is separate from the pegbody. The retaining device is configured to attach to the peg body, withat least a first portion of the retaining device above an upper surfaceof the implant plate.

In some embodiments, a method, comprises: (a) drilling at least two pegholes into a resected surface of a bone; (b) assembling at least twopegs to an implant plate, the implant plate having a plurality ofopenings, each of the two pegs having a longitudinal axis and a peg bodywith a transverse dimension in a direction normal to the longitudinalaxis, the transverse dimension larger than the plurality of openings;and (c) after step (b), attaching the implant to the bone so that the atleast two pegs are inserted in the at least two peg holes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an anterior view of a talar implant assembly according to someembodiments.

FIG. 2 is a side view of one of the peg bodies of FIG. 1.

FIG. 3 is a cross sectional view taken along section line 3-3 of FIG. 2.

FIG. 4A shows a retaining device as shown in FIG. 1.

FIG. 4B shows the peg of FIG. 2 with a locking screw as a retainingdevice.

FIG. 5 is a lateral view of a resected talus.

FIG. 6 is a superior view of a talar implant trial for sizing theimplant plate of FIG. 1.

FIG. 7 is a side view of the talar implant trial of FIG. 6 pinned to theresected talus of FIG. 5.

FIG. 8 is a side view showing the pilot hole being drilled in theresected talus using a drill guide and the talar implant trial of FIG.6.

FIG. 9 is a side view showing insertion of the peg body of FIG. 2 intothe talus of FIG. 8.

FIG. 10 is a side view showing the talus of FIG. 9 after insertion ofthe peg body.

FIG. 11 is a superior view of the talar implant plate of FIG. 1.

FIG. 12 is a side view showing the talus of FIG. 10 after positioningthe talar implant plate of FIG. 11 thereon.

FIG. 13 shows the talar implant assembly of FIG. 12 after inserting theretaining devices through holes in the plate and into the peg body.

FIG. 14 is a side view of a peg body according to some embodiments.

FIG. 15 is a cross-sectional view taken along section line 15-15 of FIG.14.

FIG. 16 shows a retaining device a retaining device suitable for usewith the peg body of FIG. 15.

FIG. 17 shows a talar implant assembly including the peg of FIGS. 14-16.

FIG. 18 is a side view of another peg body according to someembodiments.

FIG. 19 is a superior view of the peg body of FIG. 18.

FIG. 20 is an exploded view of an exemplary peg according to someembodiments.

FIG. 21 shows a talar implant assembly including the peg of FIG. 20.

FIG. 22 is a side view of an exemplary peg according to someembodiments.

DETAILED DESCRIPTION

This description of the exemplary embodiments is intended to be read inconnection with the accompanying drawings, which are to be consideredpart of the entire written description. In the description, relativeterms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,”“below,” “up,” “down,” “top” and “bottom” as well as derivative thereof(e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should beconstrued to refer to the orientation as then described or as shown inthe drawing under discussion. These relative terms are for convenienceof description and do not require that the apparatus be constructed oroperated in a particular orientation. Terms concerning attachments,coupling and the like, such as “connected” and “interconnected,” referto a relationship wherein structures are secured or attached to oneanother either directly or indirectly through intervening structures, aswell as both movable or rigid attachments or relationships, unlessexpressly described otherwise.

FIG. 1 is a schematic diagram of an exemplary implant system 100according to some embodiments of this disclosure. In particular, theimplant system 100 is a talar plate assembly 100. It should beunderstood that the implant system 100 may also be referred to herein asthe talar plate assembly 100. The exemplary implant system 100 comprisesan implant plate 130 and a plurality of independently positionable pegs120. In some embodiments, the plurality of pegs m include at least twodifferent insertion angles, at least two different peg body lengths, atleast two different peg body diameters, or at least two different pegconfigurations, or any combination of two or more of these features.FIG. 1 also shows (in phantom) a talar dome 170 mounted on the implantplate 130. The talar dome 170 has a mounting surface 172 attachable tothe implant plate 130 and an articulating surface 174 opposite themounting surface 172. The talar plate assembly 100 can be included in atotal ankle prosthesis.

The implant plate 130 is configured to be positioned on a surface of aresected bone, such as a resected talus 140. The implant plate 130 has aplurality of peg openings 132 therethrough, as best seen in FIG. 11. Theimplant plate 130 also has two or more openings 136 for receivingk-wires or pins 156. In some embodiments, as shown in FIG. 11, theopenings 136 are at the edge of the plate 130. In other embodiments, theopenings 136 are within the perimeter of the plate 130 and arecompletely surrounded by material of the plate. In other words, theopenings 136 are disposed interior to a peripheral edge of the implantplate. In some embodiments, all of the peg openings 132 of the plate 130have the same diameter. In other embodiments, the peg openings 132 varyin diameter.

The plurality of independently positionable pegs 120 are provided forattaching or securing the implant plate 130 to the resected bone 140.Each peg 120 has a longitudinal axis 123. Each peg 120 comprises a pegbody 122 adapted to be inserted into a respective peg hole 125 in theresected bone 140.

In some embodiments. the peg body 122 of at least one of the pluralityof pegs 120 has a cylindrical portion with an outer diameter 126 greaterthan an outer diameter 134 of a corresponding one of the plurality ofopenings 132. Although shown and described as cylindrical, the pegs maybe shaped triangular, square, hexagonal, or a combination thereof. Theside surface of the peg body 122 can have a textured surface. The pegbody 122 has an opening 131 with an inner wall 129 defining an interiorcavity along a longitudinal axis 123 of the peg body. In someembodiments, the opening 131 of the peg body 122 has a countersinkand/or counterbore or relief pocket 131 c for receiving a top portion127 of a retaining device 124. In some embodiments, the countersink orcounterbore 131 c has no threads, and is adapted to receive anon-locking screw 124, as shown in FIG. 3. In other embodiments, thecountersink or counterbore 131 d has threads to engage correspondingthreads in a head 127 b of a locking screw 124 b, as shown in FIG. 4B.In some embodiments, the distal portion 131 t of the opening has threadsfor receiving and engaging threads of a distal portion 128, 128 b of ascrew. In some embodiments, each peg body 122 has a transverse dimension126 in a direction normal to the longitudinal axis 123. The transversedimension 126 is larger than a diameter 134 of at least one of theplurality of openings 132 of the implant plate 130. In some embodiments,the transverse direction is an outer diameter 126 (FIG. 3) of the pegbody 122, and the outer diameter 126 of the peg body is larger than thediameter 134 of the openings 132 (FIG. 11) of the implant plate 130.

The peg 120 further comprises a retaining device 124 separate from thepeg body 122. The retaining device 124 is configured to attach to thepeg body 122, with at least a first portion 127 of the retaining device124 positioned above a lower surface 135 of the implant plate 130. Insome embodiments, the first portion 127 of the retaining device 124 ispositioned entirely within the thickness of the implant plate 130,between the lower surface 135 and the top surface 139 to ensure properseating of the talar dome onto the implant (e.g., talar) plate. In thisconfiguration, the first portion 127 does not protrude above the topsurface 139 of the implant plate 130. Countersinks, counterbores orrelief pockets on the top surface of the talar plate can allow the firstportion 127 of the retaining device to be positioned within thethickness of the implant plate 130. In some embodiments, the firstportion 127 of the retaining device 124 is positioned above a lowersurface 135 of the plate 130, and can extend slightly above an uppersurface 139 of the plate 130. In other embodiments, the first portion127 of the retaining device 124 is positioned above a upper surface 139of the plate 130, and a connecting portion 128 of the retaining device124 extends from the bottom of the countersink 131 c—or the top surface139 of the opening 131 if there is no countersink or counterbore—of theimplant plate 130 to the peg body 122.

In some embodiments, the retaining device 124 of at least one of theplurality of pegs 120 is an inner component having a proximal head 127larger in diameter or periphery than the corresponding one of theplurality of openings 132 (or diameter or inner periphery) and a distalbody 128 sized to fit through or be received within the correspondingone of the plurality of openings 132. The distal body 128 of the innercomponent 124 is configured to engage the inner wall 129 of the opening131 of the peg body 122. In some embodiments, the distal body 128 hasmale threads disposed on an outer surface thereof and the inner wall 129of opening 131 has female threads. For example, the inner wall can bethreaded, and the inner component 124 can be a screw. In someembodiments, the inner component is a non-locking screw, as shown inFIG. 4A, or a locking screw as shown in FIG. 4B.

In some embodiments, the distal body 128 has barbs disposed on an outersurface thereof, and the inner wall 129 of the opening 131 can besmooth, ridged, grooved, or barbed. In some embodiments, the distal body128 has ridges, and the inner wall 129 can be smooth, ridged, grooved,or barbed. In some embodiments, the distal body 128 has splines, and theinner wall 129 can be smooth or splined. In other embodiments, either orboth of the distal body 128 and the inner wall 129 can have a knurledsurface. In other embodiments, either or both of the distal body 128 andthe inner wall 129 can have a tapered surface.

FIGS. 2-4B show components of an exemplary peg assembly 120. In someembodiments, the peg body 122 is rotationally symmetric, and has acircular cross section in any plane, transverse to the longitudinal axis123 of the peg 120. The peg body 122 is generally bullet-shaped. Theside surface of the peg body 122 can have a textured surface. The distalend of the peg body 122 can be hemispherical, ellipsoidal, or the like.FIG. 3 is a cross-sectional view of the peg body 122 taken along sectionline 3-3 of FIG. 2. The peg body 122 has a central opening 131 with aninner wall 129. The proximal (top) portion of the inner wall 129 caninclude a countersink and/or counterbore 131 c as described above. Thedistal portion of the inner wall 129 has an outer diameter that issmaller than the diameter 134 of the openings 132 in the implant 130. Insome embodiments, the first portion 127 of the retaining device 124 isconfigured to be positioned entirely within the thickness of the implantplate 130, between the lower surface 135 and the top surface 139 toensure proper seating of the talar dome onto the talar plate.Countersinks, counterbores or relief pockets on the top surface of thetalar plate can allow the first portion 127 of the retaining device tobe positioned within the thickness of the implant plate 130. In someembodiments, the first portion 127 of the retaining device 124 isconfigured to be positioned above a lower surface 135 of the plate 130,and to extend slightly above an upper surface of the plate 130. In otherembodiments, the first portion 127 of the retaining device 124 isconfigured to be positioned above an upper surface 139 of the plate 130,and a connecting portion 128 of the retaining device 124 is configuredto be extend through one of the openings 132 from the bottom of thecountersink 131 c—or the top surface of the opening 131 if there is nocountersink or counterbore—of the implant plate 130 to the peg body 122.

In some embodiments, the inner wall 129 has a female thread with aninner diameter ID and an outer diameter OD (shown in FIG. 3), where theouter diameter is smaller than the diameter 134 of the openings 132 inthe implant 130. The inner component can be a non-locking screw 124having a head 127 with a smooth outer sidewall, as shown in FIG. 4A. Inother embodiments, the inner component can be a locking screw 124 bhaving a head 127 b with a threaded outer sidewall, as shown in FIG. 4B.The distal body 128 b of the locking screw 124 b can be the same as thedistal body 128 of the non-locking screw 124, meaning, the distal bodyof the non-locking screw 124 and the distal body of the locking screw124 b can both be threaded. In some embodiments, the retaining device124 is a polyaxial screw, configured for locking at a variety of angleswith respect to a longitudinal axis 137 of the holes 132 (shown in FIG.12). For example, in some non-limiting embodiments, the screws 124 canbe inserted at any angle within about 20 degrees of the axis 137. Forexample, the polyaxial screws can be inserted at angles from about 45,40, 35, 30, 25, 20, 15, 10, 5, and 0 degrees (°) with respect to thelongitudinal axis 137.

FIGS. 5-13 show an exemplary method for implanting the talar plateassembly 100 in a resected talus 140 (FIG. 5). FIG. 5 is a lateral viewof the resected talus 140. FIG. 6 shows a talar plate trial component150 that can be used for sizing the talar plate 130, and locating anddrilling a suitable set of peg holes 125 in the resected talus 140. Thesurgeon moves the talar plate trial component 150 into an optimalposition (adjacent the talus) by holding the handle portion 154.

In some embodiments, the final positioning of the talar construct canalso be accomplished by the “floating Talus” method. In the “floatingTalus” method the surgeon places each of a plurality of trials in thebony spaces between the resected talus and the tibia individually, andmoves the ankle joint through its full range of motion. By doing thiseach trial settle in when it reaches its optimal position, instead ofbeing directed by the surgeon to a predetermined location.

Once the talar plate trial component 150 is properly positioned, thesurgeon inserts at least two k-wires or pins 156 through the talar platetrial component 150 into the bone 140, as shown in FIG. 7.

Pilot holes are then drilled in the resected bone 140 using a drillguide 160 that allows the surgeon to vary the direction and angle of thepilot holes, as shown in FIG. 8. Each peg 120 in the plurality of pegsis adapted to be inserted at a respective angle relative to the implantplate 130, independently from the angle of each remaining peg 120 in theplurality of pegs. Thus, each pilot hole can be drilled at a respectiveangle relative to the implant plate trial 150, independently from theangle of each remaining pilot hole. Upon drilling each pilot hole, thesurgeon can inspect the quality of the bone around that hole, and if thebone quality is poor, the surgeon can fill the pilot hole with asubstrate such as bone cement, bone filler, or an autograft or allograft(e.g., synthetic bone fill material), and re-drill the pilot hole at adifferent angle and/or direction.

Once the pilot holes are all drilled, the surgeon can remove the drillguide 160 and the talar plate trial component 150. The k-wires 156remain positioned in the bone 140, to enable proper positioning andalignment of the implant plate 130. Then the implant plate 130 ispositioned on the resected bone 140, with the k-wires 156 extendingthrough the openings 136 of the implant plate 130.

Then, one of the retaining devices 124 is inserted into itscorresponding peg body 122, with at least a first portion of theretaining device 127 positioned above a bottom surface 135 of theimplant plate 130, and either a second portion 128 of the retainingdevice 124 extends to the peg body, or a portion of the peg bodypenetrates the bottom surface of a respective opening 132 in the implantplate 130. In some embodiments, the first portion 127 of the retainingdevice 124 is positioned entirely within the thickness of the implantplate 130. In some embodiments, the first portion 127 of the retainingdevice 124 is positioned above a lower surface 135 of the plate 130, andto extend slightly above an upper surface 139 of the plate 130, betweenthe lower surface 135 and the top surface 139 to ensure proper seatingof the talar dome onto the talar plate. Countersinks, counterbores orrelief pockets on the top surface of the talar plate can allow the firstportion 127 of the retaining device to be positioned within thethickness of the implant plate 130. In other embodiments, the firstportion 127 of the retaining device 124 is positioned above an uppersurface 139 of the plate 130, and a connecting portion 128 of theretaining device 124 is configured to be extend through one of theopenings 132 from the bottom of the countersink 131 c—or the top surfaceof the opening 131 if there is no countersink or counterbore—of theimplant plate 130 to the peg body 122.

As shown in FIGS. 9 and 10, in some embodiments of the method, the pegbodies 122 are inserted in the peg holes 125 before assembling the pegsto the implant plate 130. In the case where the pegs 120 or peg bodies122 are implanted at respectively different angles, the surgeon may wishto position the peg 120 or peg body 122 first within the talus, thenposition the implant plate 130 on the resected talus, aligning the holes136 of the plate 130 with the k-wires 156, which results in the holes132 of the implant plate 130 being aligned over the proximal portions ofthe pegs 120 or peg bodies 122. Then the surgeon inserts the innercomponents 124 into the peg bodies 122 from above the plate 130. (Inother embodiments, discussed below with respect to FIGS. 20-22, aproximal end 443 or 552 of the peg body 422 or 522 extends into orthrough the plate 130, and an outer component 447 or 553 is placed overthe proximal end.)

FIG. 11 is a dorsal view of the implant plate 130, including theopenings 132 and the k-wire openings 136. FIG. 12 is a lateral view ofthe bone 140 with the implant plate 130 inserted on the resected surfaceof the bone, positioning the plate 130 using the k-wires or pins 156.The implant plate 130 is positioned on the resected talus with thek-wires 156 extending through the openings 136 in the implant plate 130.The retaining devices 124 are inserted from the top side of the plate130, through each of the openings 132 and into the peg bodies 122, whichhave previously been positioned in the peg holes 125 in the embodimentof FIG. 11. The retaining devices 124 attached the peg bodies 122 to theplate 130. The top portion 127 of the retaining device 124 extends abovethe bottom surface 135 of the plate 130. In some embodiments, the topportion 127 of the retaining device 124 extends above the upper surface139 of the plate.

In an embodiment of the method as shown in FIGS. 9-12, each peg body 122is positioned independently, and then the implant plate 130 ispositioned and each retaining device 124 is driven into the peg body 122from the top side of the implant plate 130. In some situations, thisapproach may give the surgeon flexibility and ease in fitting anddriving each individual peg body 122 into the bone 170. Each peg can beindividually sized, fitted and inserted. FIG. 13 is a lateralcross-sectional view of the implant plate assembly 100 afterimplantation. After implanting the implant plate assembly 100, the talardome 170 (FIG. 1) is attached to the implant plate 130.

In other embodiments of the method, using a “back table” approach, thesurgeon or staff pre-assembles the pegs 120 to the bone 170, forming theimplant plate assembly 100 as shown in FIG. 1 before the plate 130 ispositioned on the resected bone 170. If the pegs 120 are assembled inthe back table approach, all of the pegs are oriented with their axes atthe same angle relative to the bottom surface 135 of the plate 130, andall the peg holes 125 are drilled at the same angle. The retainingdevices 124 are inserted through the openings 132 of the implant plate130 and into each of the threaded distal portions 131 t of inner walls129 of the opening 131. The pegs 120 are driven into position in the pegholes 125 by tapping on the fastening devices 124/124 b until the pegbodies 122 are completely seated within their respective peg holes 125.

In some embodiments, the outer diameter of the threads of the distalbody 128 is larger than the outer diameter of the threads in the innerwall 129 of opening 131, so that inserting the distal body 128 entirelyinto the opening 131 of the peg body 122 exerts a force in the radialdirection, causing the peg body 122 to strain or expand slightly in theradial direction and securely grip the bone 170. The strain of the pegbody 122 can be enhanced if the peg body has radial slots (shown inFIGS. 18-19) extending downward from a top surface of the peg body.

FIGS. 14-17 show another example of a peg 220 according to someembodiments. FIGS. 14-15 show the peg body 222 of peg 220. The peg body222 of at least one of a plurality of pegs 220 has a cylindrical portionwith an outer diameter 226 greater than an outer diameter 134 of acorresponding one of the plurality of openings 132 in the implant plate130. In some embodiments, each peg body 222 has a transverse dimension226 in a direction normal to the longitudinal axis 223. The transversedimension 126 is larger than a diameter 134 of at least one of theplurality of openings 132 of the implant plate 130.

The peg body 222 is rotationally symmetric, and has a circularcross-section in any plane transverse to the longitudinal axis 223 ofthe peg 220. The peg body 222 is generally bullet-shaped. In otherembodiments, the peg body 22 can be various shapes including but notlimited to triangular, hexagonal, square, elliptical, and the like. Theside surface of the peg body 222 can have a textured surface. The distalend of the peg body 222 can be hemispherical, ellipsoidal, or the like.FIG. 15 is a cross-sectional view of the peg body 222 taken alongsection line 15-15 of FIG. 14. The peg body 222 has a central opening231 with an inner wall 229. The inner wall 229 defines an interiorcavity along a longitudinal axis 223 of the peg body 222.

A retaining device 224—separate from the peg body 222—is configured toattach to the peg body 222, with at least a first portion 227 of theretaining device 224 positioned above a bottom surface 135 of theimplant plate 130 as discussed above, and a connecting portion 233 ofthe retaining device 224 extending from the proximal portion 227 of theretaining device to the peg body 222. In some embodiments, the firstportion 227 of the retaining device 224 is configured to be positionedentirely within the thickness of the implant plate 130, between thelower surface 135 and the top surface 139 to ensure proper seating ofthe talar dome onto the talar plate. Countersinks, counterbores orrelief pockets on the top surface of the talar plate can allow the firstportion 227 of the retaining device to be positioned within thethickness of the implant plate 130. In some embodiments, the firstportion 227 of the retaining device 224 is configured to be positionedabove a lower surface 135 of the plate 130, and to extend slightly abovean upper surface 139 of the plate 130. In other embodiments, the firstportion 227 of the retaining device 224 is configured to be positionedabove an upper surface 139 of the plate 130, and a connecting portion233 of the retaining device 224 is configured to be extend through oneof the openings 132 from the bottom of the countersink 131 c—or the topsurface of the opening 131 if there is no countersink—of the implantplate 130 to the peg body 222.

In some embodiments, the retaining device 224 of at least one of theplurality of pegs 220 is a unitary inner component having a proximalhead 227 larger than the corresponding one of the plurality of openings132, such that the proximal head 227 is not received within the opening231, and a distal body 228 sized to fit through the corresponding one ofthe plurality of openings 132. The distal body 228 of the innercomponent 224 is configured to engage the inner wall 229 of the opening231 of the peg body 222. In some embodiments, the distal body 228 atapered outer surface, and the inner wall 229 of opening 231 has atapered inner surface. For example, the taper can be a Morse taper. Inother embodiments, other tapers are used. In some embodiments, a narrowconnecting portion 233 connects the head 227 and the distal body 228. Inother embodiments, the connecting portion 233 is as wide as the greatesttransverse dimension of the tapered portion 224, for greater strength.

FIG. 17 shows an implant assembly 200 including the implant plate 130,the peg body 222 and the retaining device 224. As in the case of theimplant assembly 100 of FIGS. 1-13, if the largest diameter of thedistal body 228 and the connecting portion is smaller than the diameterof the openings 132 in the implant plate, the implant plate assembly 200can be implanted. First each peg body 222 is inserted into itsrespective peg hole, then the plate 130 is positioned on the resectedtalus 140, and then the retaining devices 224 are driven into thecentral opening 231 of each peg body 222.

Alternatively, the implant plate assembly 220 can be pre-assembled usingthe back table method discussed above, and all the pegs of the assemblyinserted into the bone 170 at the same time. Briefly, the implant plateassembly 220 is connected to the pegs 220 and the entire assembly ispositioned within and thereon the talus simultaneously.

In some embodiments, the retaining device 224 is unitary. In otherembodiments, the retaining device 224 has two components: the bottomcomponent includes the tapered portion 228 and the connecting portion233, which can have a male outer thread (not shown). The top portionincludes a threaded hub or cap screw 227 with a female inner thread (notshown). If the top portion 227 is a separate piece from the bottomportion 228, then the diameter of the bottom portion 228 can be greaterthan the diameter of the holes 132 of the implant plate 130.

FIGS. 18 and 19 show a variation of the tapered peg body 322. Thetapered peg body 322 is the same as the peg body 222, except that aplurality of radial slots 319 extend downward from the top surface ofthe peg body 322. The tapered slots 319 extend from the inner surface orwall of the peg body 322 to the outer, exterior surface of the peg body322 (full thickness slots). The tapered slots 319 allow the top of thepeg body 335 to deflect slightly in the radial direction when the innercomponent 224 (retaining device) is inserted into the tapered opening331 of the peg body 322. Other aspects of the structure and method ofFIGS. 18-19 are the same as discussed above with respect to FIGS. 14-17.

FIGS. 20 and 21 show another exemplary implant plate assembly 400. Theassembly 400 has an implant plate 130 and a plurality of independentlypositionable pegs 420. Each peg 420 has a peg body 422 and a retainingdevice 447. The peg body 422 is adapted to be inserted into a respectivepeg hole in the resected bone. The peg body 422 has a transversedimension 426 in a direction normal to the longitudinal axis of the pegbody. The transverse dimension 426 is larger in diameter than theplurality of openings 132 of the implant plate. In some embodiments, theretaining device 447 is positioned within the thickness of the implantplate 130, above the bottom surface 135, between the lower surface 135and the top surface 139 to ensure proper seating of the talar dome ontothe implant plate 130 (e.g., talar plate). Countersinks, counterbores orrelief pockets on the top surface of the implant plate 130 can allow theretaining device 447 to be positioned within the thickness of theimplant plate 130. For example, the retaining device 447 can fit in thecountersink or counterbore 131 c of the opening 132 in the plate 130. Inother embodiments, the retaining device 447 is positioned above an uppersurface of the plate 130, and a connecting portion 433 of the peg body422 extends from the bottom surface 135 of the plate at least part waythrough the thickness of the plate 130. The transverse dimension 426 isat a central portion of the peg body 422. In some embodiments, the pegbody 422 is round and the transverse dimension is a diameter of the pegbody. In other embodiments, the peg body has gripping features 449, suchas edges that grip bone and resist rotation of the peg body 422 if atorque is applied to the peg body 422. The side surface 448 of the pegbody 422 can have a textured surface. For example, the surface can berough or knurled, and can have barbs, or ridges. The peg body 422 can besolid, without any cavity or opening.

The peg body 422 further comprises a proximal connecting portion 433configured to extend through one of the openings 132 of the implantplate 130 from a bottom surface 135 of the implant plate 130. Forexample, in some embodiments, the peg body 422 has a thread on at leastthe connecting portion 433 of the peg body, and the retaining device isa threaded cap 447 configured to engage the thread of the connectingportion 433 when the thread extends through the corresponding one of theplurality of openings 132. Each of the plurality of openings 132 of theimplant plate 130 is configured to receive the connecting portion 433 ofthe peg body 422 at a plurality of different angles. For example, thepegs can be attached at a variety of angles from about 45, 40, 35, 30,25, 20, 15, 10, 5, and 0 degrees (°) with respect to a direction normalto the bottom surface 135 of the implant plate 130. Each peg 420 in theplurality of pegs is adapted to be inserted at a respectively differentangle relative to the implant plate 130, independently from the angle ofeach remaining peg in the plurality of pegs.

A retaining device 447 is separate from the peg body 422. The retainingdevice 447 is configured to attach to the peg body 422, with at least afirst portion of the retaining device 427 above a bottom surface 135 ofthe implant plate 130. In some embodiments, the retaining device 447 isentirely contained between the top surface 139 and the bottom surface135 of the plate 130. In other embodiments, the retaining device 447 ispartially contained between the top surface 139 and the bottom surface135 of the plate 130, and a portion of the retaining device 447 extendsabove the top surface 139. In some embodiments, as shown in FIG. 21, thepeg body 422 of at least one of the plurality of pegs 420 has acylindrical portion 448 with a diameter 426 greater than a diameter of acorresponding one of the plurality of peg holes 132; the connectingportion 433 of the peg body 422 of the at least one of the plurality ofpegs is a threaded member, the threaded member having an outer diametersmaller than a diameter of a corresponding one of the plurality ofopenings 132, and the retaining device 447 of the at least one of theplurality of pegs comprises a threaded cap configured to engage thethreaded member 433 when the threaded member extends at least partiallythrough the corresponding one of the plurality of openings 132. Animplant plate assembly 400 as shown in FIGS. 20-21 can be implantedusing the back table method discussed above, in which the pegs 420 arepre-assembled to the implant plate 130 before implanting the pegs in thepeg holes.

In other embodiments, ridges, grooves, or barbs can be substituted forthe male threads on the member 433, and the corresponding retainingdevice 447 has ridges, grooves, or barbs substituted for the femalethreads.

FIG. 22 shows an example of another peg 520 according to someembodiments. The peg body 522 has a bottom portion 548, which isgenerally bullet-shaped. The peg body 522 has a transverse dimension(e.g., diameter) 526 in a direction normal to the longitudinal axis (notlabelled) of the peg body. The transverse dimension 526 of each peg body522 is larger than its corresponding opening 132 in the implant plate130. In some embodiments, all the pegs 522 have the same diameter 526,in other embodiments, the diameters 526 vary from peg to peg. Thetransverse dimension 526 is at a central portion of the peg body 522. Insome embodiments, the peg body 526 has gripping features, such as atextured surface, which can be rough or knurled, and can have barbs, orridges. The peg body 522 can be solid, without any cavity or opening.

The connecting portion 551 of the peg body 522 of at least one of theplurality of pegs 520 has a tapered outer surface 552, the tapered outersurface 552 having a maximum outer diameter 557 smaller than a diameter134 of a corresponding one of the plurality of openings 132 in theimplant plate 130. The retaining device 553 of the peg 520 comprises atapered inner surface 555 configured to engage the tapered outer surface552 when the tapered outer surface 552 extends at least partiallythrough the corresponding one of the plurality of openings 132 of theimplant plate 130. The tapered member 551 is inserted through theimplant 130 and into the tapered inner surface 555 of the retainingdevice 553 to form a taper joint such as a Morse taper joint. In someembodiments, the retaining device 553 has a curved outer edge 559 at abottom end thereof, to allow the angle of the longitudinal axis of thepeg body 522 to vary relative to the upper surface 139 of the implantplate 130.

Although the subject matter has been described in terms of exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed broadly, to include other variants and embodiments,which may be made by those skilled in the art.

What is claimed is:
 1. An implant system, comprising: an implant plateadapted to be positioned on a surface of a resected bone, the implantplate having a plurality of openings therethrough; a plurality ofindependently positionable pegs for attaching the implant plate to theresected bone, each peg having a longitudinal axis and comprising: a pegbody adapted to be inserted into a respective peg hole in the resectedbone, the peg body having a transverse dimension in a direction normalto the longitudinal axis, the transverse dimension larger than theplurality of openings, and a retaining device separate from the pegbody, the retaining device configured to attach to the peg body, with atleast a first portion of the retaining device positioned above an uppersurface of the implant plate, and a connecting portion of the retainingdevice extending therethrough.
 2. The implant system of claim 1,wherein: the peg body of at least one of the plurality of pegs has acylindrical portion with an outer diameter greater than an outerdiameter of a corresponding one of the plurality of openings, the pegbody having an inner wall defining an interior cavity along alongitudinal axis thereof, and the retaining device of the at least oneof the plurality of pegs is an inner component having a proximal headlarger than the corresponding one of the plurality of openings and adistal body sized to fit through the corresponding one of the pluralityof openings, the body of the inner component configured to engage theinner wall of the peg body.
 3. The implant system of claim 2, whereinthe inner wall is threaded, and the inner component is a screw.
 4. Theimplant system of claim 2, wherein the inner wall has a taper and theouter peg body has a corresponding taper.
 5. The implant system of claim4, wherein the taper is a Morse taper.
 6. The implant system of claim 4,wherein the outer peg body has a plurality of radial slots extendingdownward from a top of the outer peg body, so that the outer peg body isadapted to deflect radially when the inner component is inserted intothe outer peg body.
 7. An implant system, comprising: an implant plateconfigured to be positioned on a surface of a resected bone, the implantplate having a plurality of openings therethrough; a plurality ofindependently positionable pegs for attaching the implant plate to theresected bone, each peg having a longitudinal axis and comprising: a pegbody adapted to be inserted into a respective peg hole in the resectedbone, the peg body having a transverse dimension in a direction normalto the longitudinal axis, the transverse dimension larger than adiameter of at least one of the plurality of openings, the peg bodyfurther comprising a proximal connecting portion penetrating one of theopenings of the implant plate, and a retaining device separate from thepeg body, the retaining device configured to attach to the peg body,with at least a first portion of the retaining device above an uppersurface of the implant plate.
 8. The implant system of claim 7, whereinthe transverse dimension is at a central portion of the peg body.
 9. Theimplant system of claim 8, wherein the transverse dimension is adiameter of the peg body.
 10. The implant system of claim 7, whereineach of the plurality of openings is configured to receive a secondportion of the retaining device or the connecting portion of the pegbody at a plurality of different angles.
 11. The implant system of claim10, wherein and each peg in the plurality of pegs is adapted to beinserted at a respective angle relative to the implant plate,independently from the angle of each remaining peg in the plurality ofpegs.
 12. The implant system of claim 10, wherein the implant plate is atalar plate adapted to be positioned on a surface of a resected talus.13. The implant system of claim 7, wherein each peg in the plurality ofpegs is adapted to be positioned at a respectively different angle. 14.The implant system of claim 7, wherein the peg body of the at least onepeg has a textured surface on a portion thereof.
 15. The implant systemof claim 7, wherein the peg body has a thread on at least the connectingportion of the peg body, and the retaining device is a threaded capconfigured to engage the thread of the connecting portion when thethread extends through the corresponding one of the plurality ofopenings.
 16. The implant system of claim 7, wherein: the peg body of atleast one of the plurality of pegs has a cylindrical portion with adiameter greater than a diameter of a corresponding one of the pluralityof peg holes, the connecting portion of the peg body of the at least oneof the plurality of pegs is a threaded member, the threaded memberhaving an outer diameter smaller than a diameter of a corresponding oneof the plurality of openings, and the retaining device of the at leastone of the plurality of pegs comprises a threaded cap configured toengage the threaded member when the threaded member extends through thecorresponding one of the plurality of openings.
 17. The implant systemof claim 7, wherein: the connecting portion of the peg body of the atleast one of the plurality of pegs has a tapered outer surface, thetapered outer surface having a maximum outer diameter smaller than adiameter of a corresponding one of the plurality of openings, and theretaining device of the at least one of the plurality of pegs comprisesa tapered inner surface configured to engage the tapered outer surfacewhen the tapered outer surface extends through the corresponding one ofthe plurality of openings.
 18. The implant system of claim 17, whereinthe tapered outer surface and the tapered inner surface form a Morsetaper joint.
 19. The implant system of claim 7, further comprising atalar dome having a mounting surface attachable to the implant plate andan articulating surface opposite the mounting surface.
 20. The implantsystem of claim 7, wherein the plurality of pegs includes at least oneof the group consisting of: at least two different peg body lengths, atleast two different peg body diameters, or at least two different pegconfigurations.
 21. A method, comprising: (a) drilling at least two pegholes into a resected surface of a bone; (b) assembling at least twopegs to an implant plate, the implant plate having a plurality ofopenings, each of the two pegs having a longitudinal axis and a peg bodywith a transverse dimension in a direction normal to the longitudinalaxis, the transverse dimension larger than the plurality of openings (c)inserting a screw through the implant and into the peg body of at leastone of the at least two pegs; and (d) attaching the implant to the boneso that the at least two pegs are inserted in the at least two pegholes.
 22. The method of claim 21, wherein each peg has a retainingdevice, and step (b) includes attaching the one of the peg bodies to theretaining device, with at least a first portion of the retaining devicepositioned above the implant plate, and either a second portion of theretaining device or a portion of the peg body penetrating a respectiveopening in the implant plate.
 23. The method of claim 21, wherein step(b) includes inserting a tapered member through the implant and throughthe peg body of at least one of the at least two pegs to form a Morsetaper joint.
 24. The method of claim 21, wherein step (b) includesjoining a threaded cap above the implant to a threaded member of the pegbody extending through the implant plate.